Integrated circuits utilize tungsten components as a conductive material for several different types of structures, such as transistor gates and contacts. Tungsten is typically formed by depositing a nucleation layer, and then depositing additional tungsten over the nucleation layer. The tungsten crystallizes to form a plurality of grains in the nucleation layer, and the additional tungsten grows and expands on the grains from the nucleation layer. The grains rapidly fill narrow cavities, but the fill process is much slower for wide cavities where the grains do not grow together from opposite sides. Continuing the tungsten deposition process to fill the wide cavities produces excessive overburden for the narrow cavities.
Excess deposited tungsten is typically removed by chemical mechanical planarization, and tungsten in the wide cavities is removed more rapidly than in the narrow cavities because it is more accessible to the planarization process. To further complicate the matter, the tungsten may be etched following the planarization process, and the tungsten etch rate in the wide cavities is faster than the tungsten etch rate in the narrow cavities. In some examples, 30% of manufactured integrated circuits suffer from over-etching due to large tungsten losses in wide cavities. The tungsten grains produce a rough surface, similar to sand paper, with different grains extending to different heights at the surface. The planarization process can impact individual grains and break them loose from the tungsten material, so gaps are formed. The removed grain then exposes the sides of adjacent grains to increased abrasive action, so large sections of tungsten are often removed during the planarization process.
Accordingly, it is desirable to provide integrated circuits with tungsten components having smaller grains and a smoother surface and methods for producing such integrated circuits, such that there are fewer gaps from tungsten grains removed during planarization. In addition, it is desirable to provide methods for producing integrated circuits with smaller grains of tungsten so the tungsten is deposited at a more consistent rate in wide and narrow channels. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.